Bradford-White Corp PDX Series Powered Direct Vent Gas Water Heaters, CX) Power up Sequence

PDX Series

Sequence of Operation

Power up Sequence

1

2

Start Up.

Upon power up, the control runs a safe-start check with a typical start-up delay of 1-5 seconds.

Flammable Vapor Check.

To assure no outputs are energized if the “Flammable Vapor Sensor” is out of range, the control will test the the “Flammable Vapor Sensor” for proper operating range. If the “Flammable Vapor Sensor” is within range the control resumes normal operation with no perceptible delay. If the “Flammable Vapor Sensor” is out of range, the control LED immediately flashes 7 times with 3 second pause.

Normal Heating Sequence

1Thermostat calls for heat.

2

3

4

5

Prior to energizing blower, gas control checks safety circuit to insure the circuit is open. Normal switch positions in the safety circuit are as follows:

a)Exhaust pressure switch normally open.

b)Blower temperature switch normally closed.

c)Inlet pressure switch normally closed.

If the safety circuit is closed, the control waits 4 seconds, gas control LED flashes 2 times with 3 second pause. Gas control waits 2 minutes then, blower runs for 30 seconds. This cycle repeats until safety circuit opens.

Blower energizes.

Blower pre-purge period (2 seconds)

Exhaust pressure switch proves blower/vent system operation.

a)If the pressure switch does not close within 30 seconds, the control LED Flashes 3 times with 3 second pause. The blower runs for 30 seconds every 2 minutes trying to get the pressure switch or blower temperature switch to close. This cycle repeats as long as there is a call for heat.

b)The normally closed inlet pressure switch allows the system to work as long as the inlet air is not blocked.

Trial for pilot ignition (90 seconds).

a)The gas control lights the pilot by activating spark igniter and gas flow to pilot burner.

b)If flame is not sensed within 90 seconds, igniter and gas flow are deactivated, blower will post purge and control LED flashes 6 times with 3 second pause.

6Main burner Ignition

After pilot flame is sensed, gas control activates main valve for main burner ignition. The gas control will ignore flame and pressure switch signals for 3 seconds allowing for main burner to stabilize.

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